The present invention relates to a printing apparatus and a power consumption reduction method of a printing apparatus and, more particularly, to a printing apparatus comprising a plurality of full-line-type printheads having an array of printing elements corresponding to a width of a print medium, and a power consumption reduction method of a printing apparatus.
Data output apparatuses employed by, for instance, word processors, personal computers, facsimiles or the like, include a printer for printing desired data, e.g., characters, images or the like, on a sheet-type print medium, such as paper, film or the like.
Although various methods are known for a printing method of the printer, recently an ink-jet printing method has particularly brought attention for the following reasons: ability to print without contacting a print medium such as paper, low running cost, easy color printing, low-noise operation because of its non-impact method, and so on.
Among ink-jet printing apparatuses, a widely used printing apparatus is a full-line-type printing apparatus capable of further increasing printing speed, which comprises a printhead having an array of printing elements (nozzles) corresponding to a printing area, and performs printing while conveying a print medium.
When color printing is performed by the full-line-type printing apparatus, a plurality of printheads for discharging different colors of ink are arranged in a conveyance direction of a print medium and ink is simultaneously discharged from each of the printheads so as not to decrease printing speed of the color printing.
However, because such full-line-type printing apparatus simultaneously drives a large number of nozzles, it generates a problem of large power consumption.
For instance, assuming that printing is performed at resolution of 600 dpi (600 dots per inch) with a maximum printing width, corresponding to the long side of a generally used A4-size (210 mmxc3x97297 mm) print medium, the printhead will have approximately 7000 nozzles.
A color printing apparatus using six types of ink, e.g., black, cyan, magenta, yellow, light cyan, light magenta and so on, comprises six of the aforementioned printheads. Discharging ink from each nozzle requires a driving voltage of 15V and a current of 100 mA applied for 1 xcexcS. In a case where each printhead is driven in a cycle of 62.5 xcexcS, the maximum power consumption value is:
(15Vxc3x97100 mA)xc3x97(1 xcexcS/62.5 xcexcS)xc3x977000xc3x976=1008 W≐1 kW.
In reality, the printing apparatus further requires power consumed by other electric circuits and motors or the like. Therefore, the maximum power consumption value of the printing apparatus as a whole is one thousand and several hundreds watts.
When the maximum power consumption value exceeds 1 kW, it is difficult to use the printing apparatus and other electrical equipment on the same power supply path, thus a dedicated power supply path is necessary for the printing apparatus. This limits the location of installation or form of utilization, thus causing inconvenience to users.
The present invention has been proposed in view of the above problems, and has as its object to provide a printing apparatus capable of reducing power consumption without decreasing printing speed, and provide a power consumption reduction method of a printing apparatus.
To achieve the above object, the present invention provides a printing apparatus including a plurality of full-line-type printheads having an array of printing elements corresponding to a width of a print medium, comprising: pixel number calculation means for calculating a number of pixels to be printed in a predetermined region; print power calculation means for calculating a value related to power to be supplied to the printhead based on the number of pixels; determination means for determining whether or not the value related to power is larger than a predetermined value; and thinning means for thinning a pixel to be printed in the predetermined region so as to keep the value related to power under the predetermined value, if the determination means determines that the value related to power is larger than the predetermined value.
More specifically, the printing apparatus, including a plurality of full-line-type printheads having an array of printing elements corresponding to a width of a print medium, calculates a number of pixels to be printed in a predetermined region; calculates a value related to power to be supplied to the printhead based on the number of pixels; determines whether or not the value related to power is larger than a predetermined value; and performs thinning on a pixel to be printed in the predetermined region so as to keep the value related to power under the predetermined value, if the value related to power is determined to be larger than the predetermined value.
By virtue of the present invention, the maximum power consumption value is kept under a predetermined value without decreasing printing speed. Therefore, the suppliable maximum power of a power source can be set smaller than a conventional value, and a power source device can be downsized.
Accordingly, the entire printing apparatus can be downsized, decreased in weight, and lowered in cost. Furthermore, since the amount of heat generated in the printing operation is decreased, heat produced by a printing apparatus is decreased, thus reducing adverse effects on the environment of the apparatus, such as temperature increase and so forth. Moreover, less power consumption contributes to energy conversation.
According to the present invention, it is preferable that the printing apparatus further comprises image memory for storing input image data, and that the pixel number calculation means calculates the number of pixels based on the image data inputted to the image memory, or based on the image data read out of the image memory.
Furthermore, it is preferable that the thinning means thin out a pixel to be printed in accordance with a predetermined mask pattern.
In this case, it is preferable that the mask pattern used by the thinning means be selectable from a plurality of mask patterns.
Moreover, the value related to power can be calculated based on the number of pixels to be printed for each printhead and a power consumption value consumed to drive one printing element in each printhead.
In this case, the power consumption value consumed to drive one printing element may be different in printheads.
Further, if a plurality of power supply units (power supply voltages) are provided, the value related to power can be calculated for each unit of power supply.
Moreover, the present invention is applicable in a case where the pixels are to be printed on different printing media by a plurality of printheads in a predetermined time period.
Furthermore, in order to achieve the above object, the present invention provides a power consumption reduction method of a printing apparatus, which has a plurality of full-line-type printheads having an array of printing elements corresponding to a width of a print medium, comprising: a pixel number calculation step of calculating a number of pixels to be printed in a predetermined region; a print power calculation step of calculating a value related to power to be supplied to the printhead based on the number of pixels; a determination step of determining whether or not the value related to power is larger than a predetermined value; and a thinning step of thinning a pixel to be printed in the predetermined region so as to keep the value related to power under the predetermined value, if the value related to power is determined to be larger than the predetermined value at the determination step.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.